So-called "lighter-than-air" air ships and balloons are well-known for load carrying purposes. An aircraft of this type relies on helium or some other gas which is lighter than air to create lift. Hot air balloons are also well-known and rely for buoyancy on the natural tendency of air to rise as its density decreases on heating. Generally, these known type of craft are difficult to control with precision and have not found wide application for commercial load lifting and transporting purposes.